add_subscription

THE RISK

Medium Risk

Why add_subscription needs a policy

This tool creates or adds a new subscription record, which is a reversible modification of data. It does not delete, execute code, or move money. The 'medium' severity reflects that while subscription additions are generally safe, an agent could add malicious feeds or spam feeds to a user's reader, degrading user experience and potentially exposing them to unwanted content.

From the tool's definition Tool name 'add_subscription' and description 'Adds a new feed subscription' indicate creation of a new data object (feed subscription) in the RSS reader system.

Documented attack patterns abuse exactly the kind of access add_subscription gives an agent:

POLICY

How to control add_subscription

PolicyLayer is an MCP gateway — it sits between your AI agents and RSS MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for add_subscription:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "add_subscription": {
      "limits": [
        {
          "counter": "add_subscription_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

add_subscription stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register RSS MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More RSS MCP Server tools

Destructive delete_folder Deletes a folder. This does not delete the feeds within the folder. Destructive delete_subscription Deletes one or more feed subscriptions. Write cancel_article_sharing Cancels sharing for a specific article. Write remove_tag_from_all_articles Removes a tag from all articles that have it. Write remove_tag_from_item Removes a specific tag from an article. Write share_article Marks a specific article as a shared item. Write add_tag_to_item Adds a single tag to a specific article. Write add_tags_to_item Adds multiple tags to a specific article.

All 34 RSS MCP Server tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about add_subscription

What does the add_subscription tool do? +

Adds a new feed subscription. It is categorised as a Write tool in the RSS MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add_subscription? +

Register the RSS MCP Server MCP server in PolicyLayer and add a rule for add_subscription: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches RSS MCP Server. Nothing to install.

What risk level is add_subscription? +

add_subscription is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit add_subscription? +

Yes. Add a rate_limit block to the add_subscription rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block add_subscription completely? +

Set action: deny in the PolicyLayer policy for add_subscription. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides add_subscription? +

add_subscription is provided by the RSS MCP Server MCP server (xueli-sherryli/rss-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every RSS MCP Server tool call.

Start from RSS MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →